I ordered one of those $20 battery replacement kits for my 5th generation (video) iPod that I bought in the fall of 2005. I'm not sure why I bought it other than I thought it was amazing that something so small could play video. Who knew I'd take that for granted after scoring an iPhone almost two years later.
Anyway, the battery was toast, because it has spent most of the time sitting on an Altec-Lansing speaker rig next to my bed. That's not particularly good for those batteries. You have to "exercise" them from time to time, and let them drain entirely. That, and I'm not sure the charging circuits are the smartest from that generation of technology.
The kit I bought was like any other, with the nylon tools to try and split the thing open. That did not go well. I couldn't penetrate the crack (that's what she said!), so not caring that much about the cosmetic appearance of it, I used a small screwdriver. That did get it started, but it wasn't separating the way it looked in the photos. Normally the innards stay attached to the top, not the metal enclosure. But it was coming open like that.
By the time I got it open, I realized that I had ripped the innards from the top, which was held on by small screws. That ended up not being a big deal, as there was enough of the screw mount holes left to reattach, but the latches that held on to the metal part were toast in places. The culprit, once I got it open, was that one of the rubber cushions for the hard drive was not secured well, and created a mess of stuckness that prevented me from getting it open the right way.
In any case, the old battery was bulging. A lot. That explains why the screen had a dark spot in it, because the battery was pressing against it. Lithium-ion batteries that bloat tend to catch fire, right?
So any way, I got it back together, and it looks like everything is functional. The replacement battery is actually of a higher capacity than the original, so the battery life is probably something like 15 hours for audio. Unfortunately, it doesn't quite close up entirely, but again, it's not really ever going to get hard core use. It may live in my car eventually.